Carburetor



' 'BEST AVAILABLE COPY April 15, 1941.

W. G. McCAIN CARBURETOR Filed March 25, 1940 SEARCH Root Patented Apr.15, 1941 UNITED STATES PATENT OFFICE 11 Claims.

The present invention relates to improvements in carburetors forinternal combustion engines and is hereinafter described as embodied ina carburetor of the fioatless or pressure atomizing type in which theflow of fuel from a source of supply under pressure is controlled by anautomatically actuated control valve.

It is well known that modern high speed high compression internalcombustion engines perform better with a relatively high degree ofintake suction. With carburetors of the usual construction there is aperiod immediately after the throttle valve is opened when the intensityof suction may drop substantially. It is not built up again untilgreater air flow caused by increased engine speed occurs. Not only doesthe period of low suction aifect the performance of the engine adverselybut loss of suction prevents proper vaporization of liquid fuel whenvaporization is induced by engine suction only. To overcome thisdifliculty and to provide proper vaporization under all conditions, itis the practice, particularly with high speed high compression typeengines, to employ a number of jets, at least one of which is activeduring normal running and one during low speed idling conditions in theengine. More often than not a third throttle controlled jet in a singlecarburetor is provided for increasing the ratio of the fuel in themixture fed to the engine during periods of engine acceleration. The useof a number of jets in this way renders the construction and adjustmentof the carburetor expensive and diflicult.

To avoid the use of a number of jets in a carburetor attempts have beenmade to employ a positive pressure in the fuel supply line behind asingle atomizing jet thus making the jet effective over a wider range ofengine suction intensities. Such attempts have heretofore failed becauseimproper fuel control, corresponding with all op-- erating conditions inan internal combustion engine such as used in automotive work, has notbeen provided. Unless special provision is made for controlling fuelflow with a pressure supply to the jet, the ratio of fuel to airdelivered to an engine when running slowly with no load will be the sameas when running at high speeds with no load and insufficient fuel willbe supplied to the engine when under heavy load conditions. As a result,there is loss in efilciency or dimculty in obtaining a prompt responsein the engine after opening the throttle. Prior carburetors have been sodesigned that a compromise between two ratios suited for theseconditions of operation is made. The adjustment of the fuelair mixturetherefore is not exactly suited, for either high speed eificiency orquick acceleration of the engine under load conditions. This defect hasbeen present heretofore both in a carburetor having fuel fed from afloat level chamber as well as one in which the fuel is fed to the jetunder pressure.

One object of the present invention is to provide an internal combustionengine carburetor designed more particularly for automotive work inwhich a more nearly correct fuel-air mixture ratio together with ahigher intake suction than heretofore will automatically be maintainedat all engine speeds or load conditions, regardless of increase inthrottle openings, whether the fuel fluid is fed to an atomizing jet atatmospheric pressure from a float level chamber disposed adjacent thejet or whether fed under a positive pressure. Another object of theinvention is to provide means for building up automatically andindependently of throttle opening the intensity of vacuum created in aninternal combustion engine before the speed of the engine increasessubstantially during periods of acceleration, thus rendering it easierto maintain the correct ratio of fuel in the mixture at all timeswithout the use of several jets, and obviating the necessity of making acompromise adjustment for different operating conditions or thepossibility of impeding the response of the engine to sudden throttleopening. Other objects are to so control the flow of fuel to an internalcombustion engine that effective proportioning of the fuel to air ismaintained when the fuel is fed directly to an atomizing jet underpressure throughout the full range of engine operating conditions,including stopping and starting, provision also being made to preventloss of fuel in stopping and immediate delivery of fuel in properproportion to prevent loading or choking the engine even when highlyheated in starting. Still further objects of the invention are toprovide an efficient carburetor of simple and easily manufacturedconstruction and by the use of which more nearly accurate control thanheretofore of fuel-air ratio in the mixture in accordance with thedemands of the engine under all operating conditions may be obtained.

With these and other objects in view, the present invention relates tothe provision in a carburetor for an internal combustion engine havingan air conduit, a throttle valve in the conduit and a fuel deliveringjet entering the conduit, of

an air actuated means for maintaining and building up the suction in theconduit around the jet more rapidly than caused by increase in air fromincrease in engine speed after opening the throttle valve. The suctionbeing built up more rapidly with this arrangement, causes a morethorough atomization of the fuel from the jet at a time when a largeproportion of fuel is being used. This feature of the invention alsoincludes the use of a suction controlling vane disposed close to the jetand directly connected to a static air pressure responsive device inorder that an increase of engine suction will reduce the flow of air andwill in turn increase the suction and turbulence in the carburetorconduit still further and more rapidly than caused by flow of air fromincrease in engine speed alone. In connection with this feature theratio of fuel in the mixture after throttle opening is reducedautomatically for eflicient continuous low power operating results.

These and other features of the invention will be apparent to thoseskilled in the art from the following detailed specification and claimsand by reference to the accompanying drawing, in which:

Figure l is a view in front elevation of a carburetor embodying thefeatures of the present invention together with a power driven fuel pumpshown in section as ordinarily employed with an internal combustionengine;

Figure 2 is a perspective view on a slightly enlarged scale illustratingthe controlling connections of the carburetor of Fig. 1, parts beingbroken away, shown in section and in separated relation; and

Fig. 3 is a sectional detail view on an enlarged scale illustrating theconstruction of the fuel jet and valve of the carburetor.

The carburetor illustrated in the drawing is constructed without a floatchamber, liquid fuel being supplied by an engine driven pump, indicatedat 2, through a pulsation absorbing air compression chamber 4. The pump2 is of a well known type, the pumping force of which is effectedthrough a coil spring 6, to give a substantially continuous pressure ofapproximately three pounds per square inch. From the compression chamberthe fuel passes directly to a vaporizing jet 8 arranged within an airinduction tube In disposed at right angles to the length of a tubularflanged conduit l2 fitted to be clamped against the inlet opening of aninternal combustion engine intake manifold (not shown). The conduit l2has a throttle shaft I4 disposed crosswise in bearings at the upper endof the conduit and a valve plate I6 is secured to the shaft to open orclose the entrance to the conduit. To connect the throttle shaft to theaccelerator pedal of an automobile the shaft l4 has an actuating arm I8secured at one end provided with a stop screw hearing against a lug 22formed on the side of the conduit l2 when the throttle is in closedpositions A continuous supply of air is insured in the induction tube IDby connecting it to the lower end of a bleeder tube 23, the upper end ofwhich is connected with the inside of the conduit above the throttlevalve plate I6.-

For supplying fuel to the vaporizing jet 8 in the correct proportion tothe air passing through the conduit with different throttle openings,the fuel passes from the compression chamber 4 through a tube 24 intovalve 26 having a metering pin 28 arranged to be forced by a spring 30towards the seat of the valve and the valve is arranged to be adjustedautomatically to give the correct ratio of fuel to air for all operatingconditions in the engine. To increase the supply of fuel with anincrease in flow of air past the throttle valve, there is mounted belowthe throttle shaft 14 an air actuated vane 32 secured to a vane shaft 34pivotally supported in the walls of the conduit I2 in parallel relationto the throttle shaft 14. At one side of the shaft 34 the vane 32extends nearly crosswise of the conduit and at the other side of theshaft 34 the air flow retarding portion of the vane extends at an angledownwardly along the length of the conduit. The downwardly extendingportion of the vane 32 is so arranged that it will be actuated away fromthe side of the conduit I2 towards the end of the induction tube intoparallel relation to the conduit by an increased flow of air past thethrottle and by the metering spring 30 towards the side of the conduitinto crosswise relation thereto when the flow of air is reduced. Thelocation of the vane in overhanging relation close to the jet andinduction tube causes a relatively high degree of turbulence around thejet to improve the homogeneity of the mixture produced. To prevent thevane from actually blocking the jet, 2. nib 36 projects from the end ofthe induction tube where it will be engaged by the vane. When the vanemoves towards the jet the fuel valve 23 is opened to allow more fuel toflow into the jet and become atomized.

To open the fuel valve 26 when the vane is moved towards the jet, thevane shaft 34 has secured at one end a cam 38. Cooperating with the camis a roll 39 rotatable on one arm of a two armed lever 40 secured on afuel control shaft 4| mounted in bearing lugs extending from the conduitat either side of a forked block 42 secured to the shaft 4|. The forkedsides of the block embrace the metering pin 28 between the stufilng boxfor the metering pin and an adjustable nut 44 at the upper end of themetering pin. The arrangement is such that when the flow of air swingsthe vane towards the jet, the metering pin is raised from its seat. Whenthe flow of air is reduced the vane swings back from the force of spring30. The cam 38 is cut with the right shape to increase the ratio of fuelto air with increase in amounts of air flowing past the vane 32. Withthis arrangement a rough approximation is reached for providing acombustible mixture for uniform running conditions in an internalcombustion engine. If the nut 44 is adjusted to provide an economicalmixture with a low percentage of fuel--for instance, in the ratio of 15parts of air to 1 of fuel-very poor performance by way of quick engineacceleration after opening the throttle may result. If a richer mixtureis used, in the ratio of 12 parts of air to 1 of fuel, betterperformance occurs in the engine when opening the throttle. The bestperformance is had when a mixture having a ratio of only 10 parts of airto l of fuel is used. With such a rich mixture heavy carbon deposits areformed and general ineconomy results under light load conditions.

According to the principal feature of the present invention a mixturerich in fuel is automatically provided when the throttle is opened forrapid acceleration purposes and as soon as the engine begins to respondto the new conditions imposed by wider throttle opening and greaterload, the ratio of fuel is immediately reduced. This result is obtainedby automatically causing the engine suction to be built up after J51.GAS & UQUlD CONTAC APPARATUS.

SEARCH a sudden throttle opening more rapidly than it would be built uponly by increased flow of air into tn; engine due to increased enginespeed. The 'iifcreased suction is built up by employing a staticpressure or suction responsive device in the form of a collapsible metalbellows 46 to cause the vane 32 to cut off the flow of air in part asthe engine begins to respond to throttle opening. By so doing the flowof air past the vane increases in speed so that no appreciable reductionin quantity occurs while, clue to the changed position of the vaneshaft, a smaller amount of fuel passes through the fuel valve. By thetime the engine has readjusted itself to the new conditions imposed byopening the throttle a relatively lean mixture is being provided. Alsobecause the suction is built up more rapidly than is possible byincreased engine speed alone, where the carburetor is being used with ahigh speed high compression engine of modern construction, the engineitself operates more efficiently and greater turbulence occurs in theair about the jet and in the engine manifold, so that a more nearlyuniform mixture of air and fuel takes place.

The .bellows 46 is connected to the inside of the carburetor conduit l2by an elbow 48 in order to be responsive to changes in static airsuction and pressure inside and outside the conduit respectively. Theupper closed end of the bellows is connected by a link 50 to an arm ofthe cam 38 in such relation that increases in suction inside the conduitcause the vane to close off the conduit.

To provide the correct ratio of fuel in the mixture the cam 38 is soshaped that when the engine to which the carburetor is connected is runidly under no load at various speeds, the supply of fuel will bemaintained at as small a proportion as possible for all throttleopenings throughout the range from closed to fully open position and theconnection between the cam and the bellows is arranged to give astronger effect on the vane shaft as a result of air flow than due tonormal suction values; that is, the vane can never be actuated to shutoff air flow due to suction effects on the bellows. Thus, the bellowsmodifies the movements of the vane by shifting it to one side or theother of a position determined by air flow. Under these conditions thedegree of vacuum produced by the engine will be a maximum when runningidly. If now a heavy load is applied to the engine the suction will dropslightly and the bellows will expand correspondingly, permitting thevane to open the fuel valve accordingly. The result of opening the fuelvalve is to give a greater ratio of fuel in the mixture since the flowof air is almost entirely controlled by the throttle valve when thesuction is reduced. The same result is effected by sudden throttleopening, a corresponding adjustment taking place as soon as the engineresponds to the thottle with increased revolutions. Since these actionsare entirely automatic in nature and not under the control of thethrottle, correct mixture control is obtainable at all times, causingthe highest possible efficiency results throughout the range of throttleopenings. Such results are particularly desirable with modern high speedhigh compression engines having down draft buretors where any excess ofraw unatomized fuel drops directly into the engine to be blown out onlypartially burned through the exhaust.

It is well known that when an engine is running slowly with no load, amixture richer in fuel than when under full load is required. To providea rich idling mixture the arm of the cam has threaded into it anadjustable set screw 52 arranged to touch the roll 39 While the bellows32 is contracted, as shown in Fig. 1, and lift the metering pin from itsseat the proper amount, substantially no air flowing past the vane 32 atthis time. When pressed against the roll 39, the screw 52 moves the rollaway from the cam and the vane 32 is moved to its extreme crosswiseposition in the conduit, closing the conduit. Under these conditions thethrottle is practically closed and most of the air drawn into the enginecomes through the induction tube 23. When the engine stops by shuttingoff the ignition or otherwise the bellows 46 expands and the meteringpin spring 30 closes the fuel valve completely by the movement of thecam to a position where the roll 39 fits within the recess formedbetween the cam and the screw 52, thus preserving a small supply of fuelunder compression in the chamber 4 for starting purposes.

When the throttle is moved from idling position to partly openedposition with the engine running, the suction may be reducedsufiiciently to cause the bellows to expand. In order to prevent closingof the fuel valve in such instance, by movement of the roll 39 into therecess between the cam and the screw 52, and thereby stalling theengine, an anti-stall screw 54 passing diametrically through thethrottle shaft I4 engages a rib 56 on a second arm of the lever 40, asshown in Fig. 2. As the anti-stall screw presses against the lever 40due to the rotation of the throttle shaft from engine idling position(Fig. l) to slightly open position of the throttle (Fig. 2), the fuelvalve is opened to furnish a slightly richer mixture than otherwisewould be provided and prevents the valve from being closed by decreasein suction and consequent slight expansion of the bellows to a positionwhere the roll 39 fits within the. recess of the cam 38.,

To further improve the operating characteristics of the carburetor,particularly with large throttle openings, a spring 58 is connectedbetween an arm 60 on the throttle shaft and the link 50 to which thebellows is connected. This spring is stretched when the throttle isopened suddenly and is allowed to contract when the throttle is closed,causing little or no tension to be exerted. Thus, the spring 58 tends todecrease temporarily the effect of the bellows and produces a richermixture for quick acceleration. After the accelerating period is overthe action of the increased flow of air on the vane 32 more than offsetsthe action of the bellows and causes the spring 58 to be relaxed.

With the carburetor thus disclosed, the ratio of fuel supplied to themixture will be increased with loss of suction in the engine with whichthe carburetor is employed and will be decreased with increase insuction, whether from throttle opening or from increased load on theengine. Also the suction will be maintained at a higher level generallyin the engine due to the rapidity with which the suction is built upagain after being reduced. Also since all supply of fuel is cut off whenthe engine is stopped, the effect of vaporizing the available fuel inthe carburetor, particularly in hot weather, is prevented. Consequentlya suitable supply is always ready for starting purposes and no troublefrom choking the engine in starting occurs.

The nature and scope of the invention having been indicated and aspecific embodiment having been described, what is claimed is:

1. Il a carburetor, a mixture conduit, a man ually'c'ontrolled throttlevalve in said conduit, a fuel nozzle discharging into said conduitposterior to said throttle valve, a source of fuel under pressureincluding a fuel passage to the nozzle, a fuel regulating needle valve,means resiliently urging the needle valve in a closing direction, a vanepivotally supported in the conduit between the throttle valve andnozzle, pivoted means mounted adjacent said conduit and having an armoperatively connected to the needle valve and including a lever, a camoperatively con nected to said vane and engaging said lever whereby flowof air against said vane tends to swing the same in one direction and toopen said needle valve to allow flow of fuel in accordance with air flowin the conduit, and means connected to said vane and responsive toreduction in static pressure in the conduit posterior to the throttlevalve whereby decrease in pressure tends to swing the vane in theopposite direction to reduce the needle valve opening.

2. In a carburetor, a mixture conduit, a manuall'y controlled throttlevalve in said conduit, a fuel nozzle discharging into said conduitposterior to said throttle valve, a source of fuel under pressureincluding a fuel passage to the nozzle, a fuel regulating needle valve,means urging the needle valve in a closing direction, a vane pivotallysupported in the conduit between the throttle valve and nozzle, pivotedmeans mounted adjacent said conduit and having an arm operativelyconnected to the needle valve and including a lever, a cam operativelyconnected to said vane and engaging said lever whereby flow of airagainst said vane tends to swing the same in one direction and to opensaid needle valve and allow flow of fuel in accordance with air flow inthe conduit, means responsive to reduction in static pressure in theconduit posterior to the throttle valve, said means being connected tosaid vane whereby fall in static pressure in the conduit tends to swingthe vane in the opposite direction to reduce needle valve opening, and aresilient link between the throttle and vane arranged upon opening thethrottle to swing the vane in the first direction to thereby increasethe needle valve opening and enrich the fuel mixture.

3. In a carburetor, a mixture conduit, a manually controlled throttlevalve in said conduit, a fuel nozzle discharging into said conduitposterior to said throttle valve, a source of fuel under pressureincluding a fuel passage to the nozzle, a fuel regulating needle valve,means urging the needle valve in a closing direction, a vane pivotallysupported in the conduit between the throttle valve and nozzle, pivotedmeans mounted adjacent said conduit and having an arm operativelyconnected to the needle valveand including a lever, a cam operativelyconnected to said vane and engaging said lever whereby flow of airagainst said vane tends to swing the same in one direction and to opensaid needle valve to allow flow of fuel in accordance with air flow inthe conduit, means responsive to reduction in static pressure in theconduit posterior to the throttle valve, said means being connected tosaid vane whereby fall in static pressure tends to swing the vane in theopposite direction to reduce needle valve opening, and means comprisinga second lever on said pivoted means and means movable with the throttlevalve arranged to engage said second lever when the throttle is closed,to open said fuel valve to provide idling fuel.

4. In a carburetor, a mixture conduit, a manually controlled throttlevalve in said conduit, a fuel nozzle discharging through an air chamberinto said conduit posterior to said throttle valve, a source of fuelunder pressure including a fuel passage to the nozzle, a fuel regulatingneedle valve, means resiliently urging the needle valve in a closingdirection, a vane pivotally supported in the conduit between thethrottle valve and nozzle, pivoted means mounted adjacent said conduitand having an arm operatively connected to the needle valve andincluding a lever, a cam operatively connected to said vane and engagingsaid lever whereby flow of air against said vane tends to swing the samein one direction and to open said needle valve to allow flow of fuel inaccordance with air flow in the conduit, means connected to said vaneand responsive to reduction in static pressure in the conduit posteriorto the throttle valve whereby decrease in pressure tends to swing thevane in the opposite direction to reduce the needle valve opening, and aby-pass conduit extending from the mixture conduit anterior to thethrottle to said air chamber for supplying air at substantiallyatmospheric pressure to said air chamber, whereby the discharge fromsaid nozzle is substantially unaffected by the fall in static pressureproduced in the mixture conduit.

5. In a carburetor, in combination, a mixture conduit, a manuallycontrolled throttle valve in said conduit, a fuel nozzle connected tosaid conduit posterior to said throttle, a source of fuel including afuel passage to said nozzle, a valve for controlling the flow of fuelthrough said nozzle, means for urging said valve in one direction, vanemeans responsive to air flow in the conduit between the throttle valveand nozzle, an operative connection between said vane and said fuelvalve to actuate said fuel valve in an opening direction when the vaneswings in response to air flow in the conduit, and means connected tosaid vane means and responsive to reduction in static pressure in saidconduit posterior to said throttle valve to actuate said fuel valve in aclosing direction upon fall in static pressure in the conduit.

6. A carburetor, a mixture conduit, a manually controlled throttle valvein said conduit, a fuel nozzle discharging into said conduit posteriorto said throttle valve, a source of fuel including a fuel passage to thenozzle, a fuel regulating needle valve for controlling fuel flow fromsaid nozzle, spring means for urging said needle valve in one direction,movable vane means in said conduit posterior to said throttle valve andconnected to said needle valve to move said needle valve in an openingdirection in accordance with air flow in the conduit, and meansincluding a bellows responsive to reduction in static pressure in saidconduit posterior to said throttle valve and operatively connected tosaid needle valve to move the same in a closing direction upon fall instatic pressure in the conduit.

7. In a carburetor, a mixture conduit, a manually controlled throttlevalve in said conduit, a fuel nozzle discharging into said conduitposterior to said throttle valve, a source of fuel including a fuelpassage to said nozzle, 9. fuel regulating valve having means for urgingit in one direction, a movable vane in said conduit Posterior to saidthrottle valve and movable in one direction by air flow in said conduit,an operative connection between said vane and said fuel valveio causesaid valve to be opened in accordance with changes in the air flow, astatic air pressure responsive device communicating with said conduitbetween said throttle valve and said nozzle, and having an operativeconnection to said vane and tending to move the vane in the oppositedirection, and a spring connected between said throttle valve and saidvane to provide movement of the fuel valve before the static pressuredevice operates.

8. In a carburetor, a mixture conduit, a manu ally controlled throttlevalve in said conduit, a fuel nozzle discharging into said conduitposterior to said throttle valve, a source of fuel including a fuelpassage to the nozzle, a fuel regulating needle valve having means forresiliently urging it in a closing direction, a shaft disposed in saidconduit, a vane on said shaft and responsive to changes in air flowthrough said conduit, a cam connected to the vane shaft and having arecess, a cam follower connected to the fuel valve and arranged to enterthe recess in the cam to permit movement of the fuel valve in a closingdirection when the vane moves toward a, crosswise position in theconduit, and means operatively connected to the throttle valve foropening the fuel valve and holding the follower away from the recess inthe cam during a predetermined initial opening movement of the throttlevalve.

9. A carburetor, a mixture conduit, a manually controlled throttle valvein said conduit, a fuel nozzle discharging into said conduit posteriorto said throttle valve, 2. source of fuel including a fuel passage tothe nozzle, a fuel regulating needle valve for controlling fuel flowfrom said nozzle, means for urging said needle valve in one direction,movable vane means in said conduit posterior to said throttle valve andconnected to said needle valve and tending to open said needle valve inaccordance with air flow in the conduit, said vane means comprising aportion extending generally transverse to the axis of said conduit andan elongated portion extending longitudinally of the conduit and havingan area substantially in excess of that of the transverse portion, saidtwo portions forming a continuous surface exposed to air how in theconduit, and

SEARCH means responsive to reduction in static pressure in said conduitposterior to said throttle valve and operatively connected to saidneedle valve and tending to close the same upon fall in static pressurein the conduit.

10. A carburetor, a mixture conduit, a manually controlled throttlevalve in said conduit, a fuel nozzle discharging into said conduitposterior to said throttle valve, a source of fuel including a fuelpassage to the nozzle, a fuel regulating needle valve for controllingfuel flow from said nozzle, means for urging said needle valve in onedirection, movable vane means in said conduit posterior to said throttlevalve and connected to said needle valve and tending to open said needlevalve in accordance with air flow in the conduit, said vane meanscomprising two connected sections of unequal areas disposed in angularrelation to each other and pivot means connected to said sections attheir point of divergence and serving to position the smaller sectiongenerally transverse to the axis of the conduit and the larger sectionlongitudinally of the conduit, and means responsive to reduction instatic pressure in said conduit posterior to said throttle valve andoperatively connected to said needle valve and tending to close the sameupon fall in static pressure in the conduit.

11. In a carburetor, a mixture conduit, a manually controlled throttlevalve in said conduit, a fuel nozzle discharging into said conduitposterior to said throttle valve, a source of fuel under pressureincluding a fuel passage to the nozzle, a fuel regulating needle valve,means resiliently urging the needle valve in a closing direction, a vanepivotally supported in the conduit between the throttle valve andnozzle, said vane having a first portion transverse to the conduit and alarger portion angularly related to the first and disposedlongitudinally in the conduit, a shaft for mounting said vane, saidshaft carrying a cam, a roller engaging said cam, a shaft for supportingsaid roller and connected to said needle valve to actuate said valve inresponse to movement of said vane, a flexible bellows mounted outside ofsaid conduit and. having an interior connection to said conduit, andmeans for connecting said bellows to said cam to exert a secondarycontrol on said cam in accordance with changes in static pressure insaid conduit.

WILLIAM G. MCCAIN.

ROOM

